Flowers and candles are placed in memory of Bulgarian TV journalist Viktoria Marinova in Ruse

RUSE, Bulgaria (Reuters) - Bulgarian police questioned a Romanian man about the murder of TV journalist Viktoria Marinova on Tuesday but released him without charge and the country remains under international pressure to solve the crime.

The body of the 30-year-old journalist, who police said had been raped, beaten and suffocated, was found on Saturday. The European Union and the United States have urged Bulgaria to bring the killer to justice.

"Our work is continuing. For the time being there are no facts and circumstances that we can announce. The Romanian citizen is to be released," Teodor Atanasov, the head of Danube regional police in Ruse, Marinova's hometown, told reporters.

On her last TV show, on Sept. 30, Marinova introduced two journalists who were investigating suspected corruption involving EU funds and said her own show, "Detector", on local television station NTV, would carry out similar investigations.

No link has been established to Marinova's work, but her death has angered many in the Balkans country where people are frustrated with corruption and an inefficient judiciary that has been criticised by the European Commission.

The Commission urged Bulgaria to conduct a rapid investigation and the U.S. embassy said it was shocked by the "horrific murder".

"U.S. is ready to help authorities if needed to bring the perpetrators to justice," it tweeted.

The police have said they are looking into all possible motives but the founder of Bivol.bg, whose reporters were on Marinova's last show, said he feared authorities were downplaying the likelihood of links to her work.

"I see deliberate attempts to marginalise this killing and manipulate the public opinion that Viktoria was a victim of a random attack or sexual manslaughter," Assen Yordanov said, adding that Marinova was the only TV journalist who had agreed to host his website's journalists to discuss the investigation.

Local people held a candlelight vigil overnight and many left flowers to commemorate Marinova, who left a seven-year-old daughter.

"This is extremely frustrating. We do not feel safe at all or calm when such things happen. I did not know her personally, but as a mother I can only feel for her," said 28-year-old Denitsa Peicheva.

Relatives and colleagues called on people to be patient and expressed hope that the police would soon find the perpetrators.

"There will be time for anger! Just let it not be today," they said in a statement on NTV's website.